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Re: can subqueries be executed first in SPARQL?

From: Gregory Williams <greg@evilfunhouse.com>
Date: Fri, 17 Jun 2016 15:00:51 -0700
Cc: james anderson <james@dydra.com>, public-sparql-dev@w3.org
Message-Id: <B438B068-C924-451C-A2AC-DC4BE3A7F698@evilfunhouse.com>
To: "Peter F. Patel-Schneider" <pfpschneider@gmail.com>
On Jun 17, 2016, at 2:25 PM, Peter F. Patel-Schneider <pfpschneider@gmail.com> wrote:
> 
>> 18.2.1 does not suggest that the recommendation believes that.
>> their nature is one of the things which defines a language.
> 
> 18.2.1 talks about variable scope.  However, all that it ends up doing is
> determining when certain syntactic constructs are syntactically illegal and
> determining how to translate SELECT *.  It doesn't do many of the things
> that one would think of as needed for variable scoping in a programming
> language, like determining whether a variable mention is a local or a global
> variable.
> 
> One could say that this notion of scoping is so important for SPARQL that it
> should affect the meaning of EXISTS.  For example, that only substitutions
> that are in-scope for SELECT ... should be carried through into its
> pattern.  I don't see any support for anything like this in the SPARQL 1.1
> Query specification.

Isn’t that exactly what some of the errata do? For example, [1]:

"""
The definition of Substitute should exclude varaibles not visible at the outermost level of the graph pattern. That is, a variable used inside a nested SELECT that is not in it's projection, should be considered a different variable. Similarly, with embedded NOT EXISTS/EXISTS expressions, variables used only within that expression, are "hidden" (these are an a nested "ASK" query).
"""


>> early on in this exchange, i suggested the step to formulate the tests which
>> demonstrate the significant issues and add them to the w3c [SPARQL] test
>> suite in order to set milestones.
>> once they exist, one can respond to your supposition.
> 
> How can one add tests to the W3C SPARQL test suite?

The test suite is now under the maintenance of the RDF Tests Community Group[2].

thanks,
.greg

[1] http://www.w3.org/2013/sparql-errata#errata-query-8
[2] https://w3c.github.io/rdf-tests/
Received on Friday, 17 June 2016 22:01:17 UTC

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